Effect of adrenaline on plasma concentrations of bupivacaine following intra-articular injection of bupivacaine for knee arthroscopy.

We administered 0.5% bupivacaine 30 ml either with or without adrenaline 5 micrograms ml-1 randomly to 16 healthy outpatients, to determine the efficacy of local and intra-articular local anaesthesia for knee arthroscopy and whether or not adrenaline should be added to intra-articular bupivacaine. Bupivacaine concentrations were measured in plasma obtained 15, 30, 45 and 60 min after intra-articular injection. Patients receiving bupivacaine with adrenaline had significantly smaller plasma concentrations of bupivacaine at all times than did patients receiving plain bupivacaine. The maximal concentrations of bupivacaine in the plain group (median 515 ng ml-1, range 46-875 ng ml-1) were greater than those in the adrenaline group (median 33 ng ml-1, range 7-125 ng ml-1) (P = 0.001). All patients found the anaesthetic satisfactory. We conclude that intra-articular/local anaesthesia is satisfactory for outpatient arthroscopic surgery, and that adrenaline should probably be added to bupivacaine before intra-articular injection.